The present invention relates to a method for transferring information in a safe way, in a system having a limited transfer capacity, without losing essential information.
When transferring data it can happen that the influx of information to a process exceeds the capacity of the following transfer channel. The traditional solution to problems with uneven data flow is to have a queue between the two data flows. If the influx is greater than the outflux during a limited time then you try to estimate how large the queue will have to be to be able to hold all the information until the influx is smaller than the outflux and the queue can begin to be emptied. It is customary to overdimension the queue size to be able to be reasonably certain that the queue will be sufficiently large, which often results in very large queues. In addition to the difficulty of assessing how large the queue must be there is always the risk that an unpredicted event will take place for which the queue will be too small anyway, with the result being a random loss of information.
If the influx of information is always larger than the outflux there will be a random loss of essential information irrespective of any queues.
There are, however, cases when there is no need to transfer all the information from one link to another, e.g. radar surveillance for traffic control. The essential information is the supervised vehicles (ships, airplanes etc.) position at the actual time, i.e. the essential information is the last available, up-to-date, information and the older information has lost its value and is no longer of interest.
When using the conventional queuing method for solving the problems connected with uneven information flows in cases similar to these, there is always the danger that if the queue size has been incorrectly estimated in combination with unpredictable cases for which the queue is too small or when the influx is always larger than the outflux, the information which is lost can be the desirable essential last information as well as old and anyhow unwanted information.
The conventional queuing method for solving the problem is therefore not acceptable for a safe transfer of essential information. There is often a further demand that the information should be transferred in order of priority and be retransferred if no acknowledgement is obtained.